Metering pump

ABSTRACT

The invention relates to a pump ( 10 ) with a proportional-volumetrical dosing unit for conveying a predetermined volume of a liquid in a range of less than about 1 ml in a precisely dosed manner. The pump is provided with a cavity ( 22 ) for receiving the liquid and is limited on one side by a membrane ( 20 ) that can be displaced by means of a lifting device ( 18 ) to change the cavity&#39;s volume. The pump ( 10 ) further comprises a lockable inlet valve ( 30 ) between a liquid reservoir and the cavity ( 22 ), a lockable outlet valve ( 34 ) between the cavity ( 22 ) and a liquid dispenser and a lockable air vent valve ( 32 ) between the cavity ( 22 ) and the ambient atmosphere. The pump is especially useful for applying a precise, defined and reproducible volume of a lacquer or an adhesive on the surface of a disk-shaped data carrier for generating a thin lacquer or adhesive film.

[0001] The invention relates to a pump with a proportional-volumetric dosing unit for the precisely proportionable delivery of a predetermined volume of a liquid in the range of less than for example 1 ml.

[0002] Disk-shaped data carriers of the DVD type must have extremely high planarity. To attain sufficient stability the data carriers are produced by adhering two disks, wherein conventionally one disk serves as a support disk and the other disk as the data disk proper. However, the data carriers can fundamentally also be comprised of two data disks adhered with one another.

[0003] For observing the required narrow planarity tolerances as well as additionally the plane-parallelity of the two disk surfaces during the adhesion of the disks, after the adhesion process strict attention must be paid that when joining the adhesive-coated disks no stresses are introduced into the disk composite and the disk are maintained in plane-parallel position during the adhesion process.

[0004] In particular in the case of data carriers with two data disks, such as for example with a DVD-9 or with the DVD-R currently in development, the adhesion process assumes prominent importance in so far as no stresses must be introduced into the data carrier via the adhesive layer. Apart from the selection of a suitable adhesive agent, which, for example, must not shrink during the curing, it must be assured during the application of the adhesive agent that the volume to be applied onto a disk can be dosed extremely precisely, that no air inclusions including microbubbles must be present in the applied adhesive agent, and that during the application of the adhesive agent onto the disk no drop becomes detached too early from the adhesive agent capillary tube and also that no drop emerges as post-ejecta.

[0005] A known feeding device for lacquers and adhesive agents onto disk-shaped data carriers or onto the disks to be adhered with one another of a data carrier comprises a valve controlled over the opening time. Such valve controls are dependent on the delivery pressure as well as on the viscosity of the lacquer or the adhesive agent. Due to the pressure loss in the feeding lines as well as to temperature fluctuations such a system must be readjusted from time to time in time-consuming manual labor.

[0006] The invention is therefore based on the task of providing a pump of the above described type, with which a predetermined liquid volume can be delivered in precisely dosable quantities. The pump in particular is to make possible the reproducible application of a predetermined volume-of lacquer or adhesive agent onto the surface of a data carrier or onto a disk intended for the production of the data carrier.

[0007] The solution according to the invention of the task comprises that the pump has a cavity receiving the liquid and the cavity is delimited on one side by a face, which is movable by a lifting device for the purpose of varying the volume of cavity and that the pump comprises an inlet check valve between a liquid storage and the cavity, an outlet check valve between the cavity and a liquid dispenser and a venting check valve between the cavity and the ambient atmosphere.

[0008] With the disposition according to the invention of a venting valve between the cavity and the ambient atmosphere the cavity during operation with liquid can be freed of air bubbles. Simultaneously with this venting process, in which the face delimiting the cavity on one side starts moving from a starting position, the volume-proportional liquid delivery can commence, which only after a specific initial phase of the movement extends reproducibly linearly. With the venting valve thus the nonlinear range, observed at the beginning of the delivery process, can be excluded in simple manner thereby that the venting valve remains open until the liquid delivery has reached the linear range.

[0009] The cavity access to the venting valve is usefully connected with the highest position of the cavity.

[0010] An especially compact and precisely operating embodiment of the pump according to the invention comprises a proportional magnet whose coil core is developed at one end as a plunger, wherein the plunger is in contact on an actuation piston with which the face delimiting the cavity on one side can be moved.

[0011] The face delimiting the cavity on one side is preferably a diaphragm clamped in at the margin such that it is fluid-tight.

[0012] The actuation piston can be automatically resettable via a reset spring. A setting optimal forgiven conditions such as composition of the liquid, delivery quantity and the like parameters, of a precisely defined and reproducible liquid volume is attained through a store-programmable control (SPS).

[0013] A special application purpose of the pump according to the invention comprises the precise, defined and reproducible application of a predetermined volume of a lacquer or of an adhesive agent onto a surface of a disk-shaped data carrier or of a disk intended for the production of the data carrier, to generate a thin lacquer or adhesive film.

[0014] Further advantages, characteristics and details of the invention are evident based on the following description of preferred embodiment examples as well as in conjunction with the drawing. Therein depict:

[0015]FIG. 1 a partially sectioned side view of a metering pump,

[0016]FIG. 2 a top view onto the metering pump of FIG. 1,

[0017]FIG. 3 a portion of FIG. 1 at an enlarged scale.

[0018] A metering pump 10 depicted in FIGS. 1 to 3 for delivering an adhesive agent from a storage container to a dispensing line with dispensing capillary tube for the application of the adhesive agent onto a disk for the production of a data carrier of DVD type (not shown in the drawing) comprised of two disks adhered to one another comprises a proportional magnet 12 whose coil core is developed at one end to form a plunger 14. In the present example the control of the plunger stroke takes place through the direct driving of the proportional magnet 12 via electric connections 16. With an alternative stroke control of the plunger 14 it can additionally be operationally connected with a displacement transducer. The plunger 14 is in contact on an actuation piston 18. The actuation piston 18 is connected at the end removed from the plunger 14 with a diaphragm 20 clamped in at the side. The diaphragm 20 delimits on one side a cavity 22 for receiving a specific quantity of adhesive agent.

[0019] Through the axial movement of the actuation piston 18 the diaphragm 20 is moved and the volume of the cavity 22—as a function of the stroke of the plunger 14—increased or decreased depending on the direction of the movement. On the surface of the cavity 22 opposing the diaphragm 20 terminate three lines 24-24′, 26-26′, 28-28′. The first line 24-24′ is connected via an interconnected inlet valve 30 with a storage container (not shown in the drawing) for the adhesive agent. The second line 26-26′ is connected with the ambient atmosphere via an interconnected venting valve 32. The third line 28-28′ is connected via an interconnected outlet valve 34 with a dispensing line (not shown in the drawing) with a dispensing capillary tube for applying the adhesive agent onto one DVD half.

[0020] The lines 24′, 26′ leading away from the metering pump 10 are for example comprised of a PTFE hose and are connected fluid-tight with the valves 30, 32, 34 via screw-type nipples 36. The electrical connections of the electromagnetically actuatable valves 30, 32, 34 are completed via flanged plugs 38.

[0021] In normal operation of the metering pump 10 the cavity 22 is always filled with adhesive agent and is substantially free of air inclusions. Extremely fine air bubbles potentially still present collect in the cavity 22 at its highest position 40 at which the venting valve 32 terminates. Before the start of the dosing process proper, the actuation piston 18 for the diaphragm 20 is in its initial position. During a first short stroke phase the venting valve 32 is opened such that potential air inclusions which have collected at the highest position 40 of the cavity 22 are removed via line 26-26′ from cavity 22. After this start-up phase, during which the characteristic of the proportional magnet 12 still exhibits an undefined and nonreproducible course, the venting valve 32 is closed and the outlet valve 34 is opened. Through the further stroke of the actuation piston 18, which now has a linear characteristic, the precise proportional volumetric dosing of the adhesive agent takes place, which is supplied on line 28-28′ via a filter to the dispensing line or to the dispensing capillary tube of an application station.

[0022] After the application of the adhesive agent onto a DVD half has been completed, the outlet valve 34 is closed. Depending on the size of the cavity 22 and the quantity of adhesive agent output with each adhesive agent application cycle from cavity 22, the above described dispensing process is repeated several times until the increasingly decreasing cavity 22 must again be replenished with new adhesive agent. It is understood that the replenishing of the cavity 22 also occurs after each adhesive agent application cycle. For this purpose the inlet valve 30 is opened while the outlet valve 34 is closed and the venting valve 32 is likewise closed. In this position of valves 30, 32, 34 adhesive agent is replenished in the cavity 22 from the storage container (not shown in the drawing) which is under a slight overpressure. This replenishment process is reinforced through the automatic reset of the actuation piston 18 which takes place via a reset spring 42. After the cavity 22 is again completely filled with adhesive agent, the next dosing process—as stated above—can be initiated.

[0023] The control of the dosing pump 10 and of the valves 30, 32, 34 takes place with high precision and in practice in real time by means of a computer via a store-programmable control (SPS). 

1. Pump with a proportional volumetric dosing unit for the precisely dosable delivery of a predetermined volume of a liquid in a range of less than approximately 1 ml, characterized in that the pump (10) comprises a cavity (22) for receiving the liquid and the cavity (22) is delimited on one side by a face (20), which for varying the cavity volume is movable by means of a lifting device (18), and that the pump (10) comprises an inlet check valve (30) between a liquid storage and the cavity (22), an outlet check valve (34) between the cavity (22) and a liquid dispenser and a venting check valve (32) between the cavity (22) and the ambient atmosphere.
 2. Pump as claimed in claim 1, characterized in that the cavity-side access to the venting valve (32) is connected with the highest position (40) of the cavity (22).
 3. Pump as claimed in claim 1 or 2, characterized in that it comprises a proportional magnet (12), whose coil core is formed at one end as a plunger (14) with the plunger (14) being in contact on an actuation piston (18) with which the face (20) is movable.
 4. Pump as claimed in claim 3, characterized in that the face delimiting the cavity (22) on one side, is a diaphragm (20) which is clamped in fluid-tight at the margin side.
 5. Pump as claimed in one of claims 3 or 4, characterized in that the actuation piston (18) is automatically resettable via a reset spring (42).
 6. Pump as claimed in one of claims 1 to 5, characterized in that it comprises a store-programmable control (SPS).
 7. Use of a pump (10) as claimed in one of claims 1 to 6 for the precise, defined and reproducible application of a predetermined volume of a lacquer or an adhesive agent onto a surface of a disk-shaped data carrier for generating a thin lacquer or adhesive agent film. 